A flexible container at an initial volume of 8.15 L contains 2.51 mol of gas. More gas is then added to the container until it reaches a final volume of 12.1 L. Assuming the pressure and temperature of the gas remain constant, calculate the number of moles of gas added to the container.

Answer 1

The easy way to do this is to recognize that you use PV = nRT and that P, R, and T are constant; therefore we can re-write the equation as k1V = n*k2*k3 or
V = n*k2k3/k1 and since k2k3/k1 is just another constant we can re-write that as V = nk. Solve for k = V/n - 8.1/2.51 = ?

Then n = V/k = 12.1/k from above = ?. Subtract this last n - first n to find how much was added.